Question

Match the sum or difference on the left to its best estimate on the right.

• A. $130$
• B. $40$
• C. $50$
• D. $30$

Answer 1

We find the nearest multiples of 10 of the numbers involved to find the best estimates of the sums or differences given.

$6160+\underset{–}{67}\to +\underset{–}{70}\underset{–}{128}\underset{–}{130}$

$\therefore$ The best estimate for $61+67$ is 130.

$9290-\underset{–}{54}\to -\underset{–}{50}\underset{–}{38}\underset{–}{40}$

$\therefore$ The best estimate for $92-54$ is 40.

$6770-\underset{–}{19}\to -\underset{–}{20}\underset{–}{48}\underset{–}{50}$

$\therefore$ The best estimate for $67-19$ is 50.

$5660-\underset{–}{29}\to -\underset{–}{30}\underset{–}{27}\underset{–}{30}$

$\therefore$ The best estimate for $56-29$ is 30.